Wireless communication systems are widely spread all over the world to provide various types of communication services such as voice or data. In general, the wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of the multiple access system include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, etc.
In general, a wireless communication system uses one bandwidth for data transmission. For example, a 2nd generation wireless communication system uses a bandwidth of 200 KHz to 1.25 MHz, and a 3rd generation wireless communication system uses a bandwidth of 5 MHz to 10 MHz. To support growing transmission capacity, the 3GPP LTE or the 802.16m has recently expanded its bandwidth to 20 MHz or higher. It may be necessary to increase the bandwidth to obtain high transmission capacity. However, if a large bandwidth is supported even when a service request level is low, it may cause significantly great power consumption.
Therefore, a multiple-carrier system capable of transmitting and/or receiving broadband data by using a plurality of carriers has been introduced by defining a carrier having one bandwidth and a center frequency. By using one or more carriers, a narrowband and a broadband are supported at the same time. For example, if one carrier corresponds to a bandwidth of 5 MHz, four carriers are used to support a bandwidth of up to 20 MHz.
It may be ineffective to directly use a control channel designed by considering only one carrier to the multiple-carrier system. Therefore, there is a need for an effective design of the control channel in the multiple-carrier system.